Without endorsing Frame or his covenant theology as a whole (see here for example regarding his “universal covenant”), note Frame’s comments about the New Covenant.
[T]he work of Christ is the source of all human salvation from sin: the salvation of Adam and Eve, of Noah, of Abraham, of Moses, of David, and of all of Godâ’s people in every age, past, present, or future. Everyone who has ever been saved has been saved through the new covenant in Christ. Everyone who is saved receives a new heart, a heart of obedience, through the new covenant work of Christ. So though it is a new covenant, it is also the oldest, the temporal expression of the pactum salutis…
Of the covenants we have discussed, most are time-specific. The Noachic Covenant begins at a specific time, when Noah builds an altar to the Lord after the flood (Gen. 8:20-9:17). Before that there was no Noachic Covenant, though we all benefit from its provisions until the final judgment. Similarly for the Covenant of Grace (Gen. 3:14-19), the Abrahamic Covenant (Gen. 12:1-3, 15:1-21, 17:1-21), the Mosaic Covenant (Ex. 19:1-9, 20:21), and the Davidic Covenant (2 Sam. 7:4-17).
But three of the covenants I have described above are not time-specific in this way: the Eternal Covenant of Redemption (the pactum salutis), the Universal Covenant, and the New Covenant. All believers partake equally in the benefits of these three covenants, regardless of when in time they live.
The Eternal Covenant of Redemption is entirely supra-temporal, so it has no beginning in time, no datable ratification ceremony. Its benefits come to all of those of all times who are elect in Christ. The Universal Covenant also has no temporal restriction. God is always creator and lord, so this covenant is always in effect.
The New Covenant does have a temporal inauguration. Covenants are typically inaugurated by the shedding of blood, and that is certainly the case with the New Covenant, by the blood of Christ, the blood that fulfills all the blood of bulls and goats in the other covenants.
But when Christ appeared as a high priest of the good things that have come, then through the greater and more perfect tent (not made with hands, that is, not of this creation) 12 he entered once for all into the holy places, not by means of the blood of goats and calves but by means of his own blood, thus securing an eternal redemption. 13 For if the blood of goats and bulls, and the sprinkling of defiled persons with the ashes of a heifer, sanctify for the purification of the flesh, 14 how much more will the blood of Christ, who through the eternal Spirit offered himself without blemish to God, purify our conscience from dead works to serve the living God. (Heb 9:11-14)
This passage follows the writer’s quotation from the New Covenant passage in Jeremiah (Heb. 8:8-12). So the shedding of Jesus’ blood, a datable historical event, is the substance of the New Covenant, the Covenant that purifies, not only the flesh, but the conscience, the heart.
Nevertheless, as we saw earlier, the efficacy of the New Covenant, unlike that of previous covenants, extends to God’s elect prior to Jesus’ atonement. When believers in the Old Testament experienced “circumcision of the heart,” or when they were Jews “inwardly,” they were partaking of the power of the New Covenant.
Compare also with Frame on Heb 8:11
Similarly, Niell argues that the special knowledge of God characteristic of the new covenant (Heb. 8:11) consists only in the change from the Old Testament priestly-sacrificial system (by which believers were taught in that era) to the teaching of the fulfillment of those ceremonies in Christ. Therefore, he argues that the membership of the new covenant is not limited to the elect. I am inclined, rather, to see the new knowledge of verse 11 as more extensive than this, including a more pervasive internal work of the Holy Spirit in God’s people, which would suggest that only the elect are fully “in” the covenant.Foreword to Sandlin, ed., Backbone of the Bible